/Engine/Source/Runtime/Engine/Classes/Materials/MaterialExpression.h
Recursively gets a list of all expressions that are connected to this Checks for repeats so that it can't end up in an infinite loop
Whether a repeat was found while getting expressions
bool GetAllInputExpressions ( [TArray](API\Runtime\Core\Containers\TArray)< [UMaterialExpression](API\Runtime\Engine\Materials\UMaterialExpression) * > & InputExpressions )